1. Field of Invention
The invention relates to a control device and a method of controlling a vehicle. In particular, the invention relates to a technology of performing a torque-boost increase control of a power source during a torque phase of an upshift when causing an automatic transmission to upshift.
2. Description of Related Art
It is known that when an automatic transmission upshifts, the drive force is dropped (is reduced) during the torque phase; the drive force the increases during the transition from the torque phase to the inertia phase, thereby generating a torque shock. To suppress such a shock during a shift, one solution is to boost the torque-boost during the torque phase.
Japanese Patent Application Publication No. JP-A-2004-316838 describes a shift control device of an automatic transmission that boosts the torque from a power source in order to cause the gear shift to progress as planned. This shift control device includes: a power source torque upper limit calculator that determines the torque upper limit of the torque that can be generated by the power source during a gear shift at the time of command of the gear shift, a power source torque-boost calculator that determines the torque generation demanded of the power source when the torque is boosted at the time of the gear shift command, a target engaging force setting section that sets a target engaging force of a shift-purpose friction element that is to be changed in state, at the time of the shift on the basis of the power source torque upper limit if it is determined that the torque-boost-time power source torque exceeds the power source torque upper limit, a power source torque control portion that controls the power source during the shift so that the output torque becomes equal to the torque upper limit, if the torque-boost-time power source torque exceeds the power source torque upper limit, and a friction element fastening control portion that controls the fastening of the shift-purpose friction element during the shift so that the engaging force becomes equal to the target engaging force, if the power source torque-boost exceeds the power source torque upper limit.
According to the shift control device described in JP-A-2004-316838, an insufficient torque-boost due to the torque upper limit of the power source is compensated for by correcting the engaging force of the friction element, and this correction is performed through a feed-forward control. Therefore, even though the object of correction is the engaging force of the friction element, the problems related to the low response in the case where the control is through a feedback control do not occur, and the height of the output torque step immediately following the torque phase during the shift can be made small.
When the accelerator operation amount is large and the power source is operating under a high load, the intake air amount cannot easily be increased even if the degree of throttle opening is enlarged. Therefore, the torque is not easily increased even in response to a torque-boost command. Therefore, if the control mode during a shift is changed in response to the torque of the power source exceeding the upper limit value as in the shift control device described in Japanese Patent Application Publication No. JP-A-2004-316838, the control mode during a shift can suddenly change at a certain accelerator operation amount. In such a case, discomfort can be caused to the driver.